How much damage would you say cometary bombardment would do to a planet? If I wanted to throw comets at a planet, what skills would I use?_________________"I’m telling you, you’ll never have a deeper sleep than curled up in a Wookie’s lap."
“We're going to win this war, not by fighting what we hate, but saving what we love.”
http://rpgcrank.blogspot.com/

Yes I have thought of this before. In fact many backwards adventurer hassling low and mid-tech Traveller planets owe their continued existence to the fact that in that Universe industrial grade civilian tractor beams aren't a thing

Also you may wish to peruse Goroth Slave of the Empire and SW Adventure Journal #15 "Tasariq: The Crystal Planet"._________________"Hey sith happens..."

Meteors say up to VW bug size impact the earth and moon on occasion, doing some decent damage. Check out the one that hit Cerblinzk to see how big of an impact craiter it caused.._________________Confuscious sayeth, don't wash cat while drunk!

So back to the original question - a cometary bombardment, unmitigated (such as by planetary shields), could do everything from change the climate of the planet, through complete destruction of the entire biosphere, to basically glassing the surface of the planet. And, if we can get some real speed going (for instance by artificially accelerating a Kuiper belt or Oort cloud object for a while, and then provide some terminal guidance), we should be able to completely shatter a planet.

So, shattering an Earth-sized planet would require energy on the order of the gravitational binding energy of the planet. For Earth, that is about 10 to the power of 32 J. An object massing 1000 tons travelling at 0.7c is about 10 to the power of 22 J, so you'll need something bigger to shatter a planet. Orcus is a trans-Neptunian object weighing in at about 10 to the power of 20 kg, which might be a more suitable bullet if you wanted to shatter a planet. We'd get something like 10 to the power of 28 J, which wouldn't completely shatter the planet, but would probably tear it up pretty bad.

One thing imo that would need to be figured out is what sort of strength rating for a tractor beam would be needed to arrest / stop / divert comments of varing size?
Ie would a Comet roughly 40-60m need only a 2d SF scale tractor beam to divert it, 4d to slow/arrest it and 6d to stop it entirely?
What about one say the size of the empire state building?_________________Confuscious sayeth, don't wash cat while drunk!

Im assuming this is connected to your rogue Ithorian terraformer. That being the case, I'm not sure a straight comet bombard is what you're looking for, as it would cause a lot of long-term damage to the planet itself. Instead, I'd suggest using a large cargo ship to harvest smaller cometary bodies (15-20 meter range), then put the comets one at a time into a shallow reentry trajectory, so that the ice that makes up the comet boils off into water vapor in the upper atmosphere. Do this enough times with enough ice-balls, and you will increase the overall water content of the planet's atmosphere._________________"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

Im assuming this is connected to your rogue Ithorian terraformer. That being the case, I'm not sure a straight comet bombard is what you're looking for, as it would cause a lot of long-term damage to the planet itself. Instead, I'd suggest using a large cargo ship to harvest smaller cometary bodies (15-20 meter range), then put the comets one at a time into a shallow reentry trajectory, so that the ice that makes up the comet boils off into water vapor in the upper atmosphere. Do this enough times with enough ice-balls, and you will increase the overall water content of the planet's atmosphere.

A bit. But Welmo isn't precisely sane; as Kytross observed, he's (unintentionally) a Bond villain, written into Star Wars._________________"I’m telling you, you’ll never have a deeper sleep than curled up in a Wookie’s lap."
“We're going to win this war, not by fighting what we hate, but saving what we love.”
http://rpgcrank.blogspot.com/